1. Field of the Invention
The subject invention generally relates to detection of a thermal event and more particularly relates to early detection of a battery cell thermal event within a battery module for use in an electric vehicle.
2. Description of Related Art
It is well known in the prior art to use electric automobiles to provide transportation for occupants. Many of these prior art electric automobiles carry several thousand pounds of nickel metal hydride batteries to achieve a long range electric vehicle for every day use by consumers. Furthermore, many of these prior art electric vehicles need to be physically large and heavy to accommodate all of these batteries, such that these cars are not capable of achieving necessary acceleration, handling, performance and an extended range needed for an electric car to become a feasible option for public purchase and use. Many prior art electrical vehicles are of normal size and not overly heavy in a very small range, thus reducing feasibility for large mass selling of such vehicles to the consuming public. Furthermore, many of these prior art electric vehicles which use such batteries had problems with protecting the occupants in the vehicle from the high voltage components and high temperatures that emanate from such high voltage components and still provide a vehicle that travels at acceptable speeds comparable to that of a gasoline or diesel internal combustion engine. Many of these prior art electrical vehicles have had problems with the prior art batteries overheating, thus reducing the range of the electric vehicle, the durability and overall life of the batteries or cells that are part of the battery pack systems within the electric vehicle.
Generally, the battery or cells arranged within many prior art vehicles operate with high power output which increases the temperature and hence, may reduce the longevity of these prior art batteries. The use of the heavy and high voltage batteries systems of the prior art electric cars required a lot of maintenance to keep the batteries operating due to the high temperatures at which the battery pack systems operated. Some of these prior art systems tried to maximize longevity of the batteries by using air cooled systems that would blow cold air over the batteries and remove unnecessary heat from the battery compartment. Some other systems use other cooling techniques to try and keep a consistent temperature for the battery cells and overall battery pack within these prior art systems. Generally, in many of these prior art vehicles if one cell of the battery overheats, such overheating of one cell may propagate to surroundings cells thus creating a thermal runaway event for the battery pack of the electric vehicle. However, some of these prior art systems were able to detect the overheating of individual cells within the battery pack after a combustion event occurs and then initiate mitigation of such thermal runaway events. Therefore, the earlier the detection of a thermal event of an individual cell within a battery module, the more effective the mitigation process would be to prevent an all out thermal runaway event for the battery module.
Therefore, there is a need in the art for an improved early detection process for a battery cell having a thermal event within a battery module. There also is a need in the art for an improved apparatus for detecting thermal events at an earlier time than prior art systems. There also is a need in the art for an early detection thermal event system that uses an optical pyrometer to determine if a battery cell has a temperature greater than a predetermined threshold. There also is a need in the art for an early detection system that will increase the maximum longevity, efficiency and power that can be extracted from the battery cells within a battery module thus increasing the range of an electric vehicle for the consumer. There also is a need in the art for a thermal event early detection system that will allow for early intervention via mitigation processes such as full active cooling of a battery module or decreasing the power demand from the surrounding cells of a runaway cell.